Genitofemoral Nerve

Fig. 6.1 Schematic drawing of the right genitofemoral nerve and its course.

(Reproduced with permission from Gilroy AM, Ross LM, MacPherson BR, Schuenke M, Schulte E, Schumacher U. Atlas of Anatomy. New York, NY: Thieme Medical Publishers; 2008. Illustration by Karl Wesker.)

Fig. 6.2 Right-sided cadaveric dissection noting the genitofemoral nerve (right arrow). The arrow is at the nerve just prior to its branching into genital and femoral branches. Note the psoas fascia over psoas major and the right ureter (left arrow). For reference, the inferior vena cava is just medial to the ureter, and lateral to the psoas major muscle are the larger femoral nerve and smaller lateral femoral cutaneous nerve.

6.2 Anatomy and Variations

The genitofemoral nerve is formed within the psoas major muscle, and is derived from both the first and second lumbar nerves. When comparing these contributions, the vast majority arise from the second lumbar nerve, although the genitofemoral nerve does receive some input from the first lumbar nerve as well as connecting fibers between L1 and L2. ¹^, ³ Once having formed within the psoas muscle, the genitofemoral nerve emerges from the psoas muscle at the L3–L4 vertebral level and travels obliquely and inferiorly. At this point, the genitofemoral nerve lies on fascia that covers the anterior surface of the psoas muscle. ¹^, ⁸ It then divides into an internal or genital branch, and an external or femoral (crural) branch. This point of division can occur at variable heights, but most often is at a point proximal to the inguinal ligament and shortly after crossing the ureter posteriorly. ¹^, ²^, ³ In some cases, it divides closer to its origin from the plexus, in which case the two separate branches will travel through the psoas muscle along varying trajectories. ¹^, ³^, ⁴

The genital branch of the genitofemoral nerve (also termed the external spermatic nerve in males) is found upon or near the external iliac artery where it crosses the lower part of that vessel. It then enters the deep inguinal ring after perforating the transversalis fascia and follows the spermatic cord in males or the round ligament in females. At this point, the genital branch goes on to supply the cremaster muscle in males and supplies cutaneous innervation of the external genitalia in both males and females. ¹^, ²^, ³ The femoral branch (crural branch) descends down the psoas muscle and lateral to the external iliac artery. It then crosses over the deep circumflex iliac artery and passes behind the inguinal ligament on its descent to enter the femoral sheath, which lies lateral to the femoral artery. ¹^, ²^, ³^, ⁴^, ⁵ The femoral branch has been shown to have communications with the middle cutaneous branch of the anterior femoral nerve, and some supporting filaments may connect it to the femoral artery. ¹

It is important to be aware of the anatomical variations that can exist in the origin, course, and point of division of the genitofemoral nerve as it can be affected by iatrogenic injury during certain procedures, especially abdominal incisions. ⁸ Variations may exist in the division of this nerve, as the genital and femoral branches may arise independently from the lumbar plexus in certain individuals. Occasionally, the genital branch may be derived from the last thoracic and first lumbar nerves. ¹ Another variation that may be seen is the absence of one division completely, or the whole nerve altogether. In these cases, the fibers that normally contribute to the genitofemoral branch will have instead joined another nerve. The fibers that usually form the genital branch may be associated with the ilioinguinal nerve, and the fibers that normally contribute to the femoral nerve may be connected with the cutaneous branches of the femoral nerve. ¹^, ³

The genitofemoral nerve may also penetrate the psoas major muscle at varying distances and locations. An analysis by Rab and colleagues showed that in roughly two-thirds of sampled specimens, the nerve is seen as a single nerve trunk penetrating the psoas muscle at a distance between 4 to 12 cm from the sacral prominence. After traveling an average of 7 cm (±3.5 cm), it divides into its two branches. In the remaining one-third of specimens, the branches were observed to penetrate the psoas muscle separately and descend as separate nerve fibers. In these cases, the distance between the site of penetration and the sacral prominence ranged from 1.5 to 13 cm for the femoral branch, and from 4 to 13 cm for the genital branch. ⁴

Of particular significance for surgeons are variations in the course of the genitofemoral nerve as it courses through the lower abdominal and pelvic regions. Three varying trajectories of the genitofemoral nerve have been distinguished on the basis of the nerve’s course along the psoas major muscle. ⁹

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